1. Field of the Invention
The invention relates generally to wellbore packer assemblies and, in particular aspects, to the design of sealing elements that are carried upon such packer assemblies.
2. Description of the Related Art
Traditional packers are comprised of an elastomeric sealing element and at least one mechanically set slip. Typically, a setting tool is run in with the packer to set it. The setting can be accomplished hydraulically due to relative movement created by the setting tool when subjected to applied pressure. This relative movement causes the slips to ride up on cones and extend into biting engagement with the surrounding tubular. At the same time, the sealing element is compressed into sealing contact with the surrounding tubular. The object of sealing elements in general is to seal fluid pressure between the outer radial surface of a packer and the internal surface of a surrounding casing or tubing.
Elastomeric sealing elements have traditionally been used with packer devices because they are able to be energized into a compressive sealing position against a surrounding tubular member. However, elastomers are vulnerable to extreme temperatures and many chemicals that are often present in wellbores. As a result, they can degrade over time and lose the ability to provide an effective seal.
Thermoplastic polymers, such as TEFLON® (polytetrafluoroethylene) polymer or PEEK (polyetheretherkeytone), have not traditionally been considered to be good candidates for use as a packer sealing element. These materials, while resistant to chemical attack and able to withstand extreme temperatures, are relatively stiff and difficult to urge into a sealing engagement that is lasting. Attempts have been made in the past to form sealing elements from a thermoplastic such as TEFLON® (polytetrafluoroethylene) polymer. U.S. Pat. No. 4,548,265, issued to Luke, for example, describes a thermal packer that is used in welibores that are expected to have high temperatures and pressure conditions. The '265 patent is owned by the assignee of the present invention and is herein incorporated by reference. The thermal packer in the Luke patent, however, uses a non-resilient, non-energizing, multi-component packing assembly. As such, it is not useful for long term sealing arrangements because it cannot be effectively energized into a sealing position.
The present invention addresses the problems of the prior art.